Would it be petty to break up for this reason or is it not my business?

My boyfriend is friends with this guy and a girl, I met both of them on different occasions. His girl friend is married while the his guy friend is single. They've been hooking up together and my boyfriend supposedly was the one who set them up together. My boyfriend brung me around both of them in the past but I had no they were messing around. I knew nothing about it until the word got out and its making me look at my boyfriend different.

Would it be petty to break up for this reason or is it not my business?
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